In underground reservoirs for hydrocarbons, water, natural gas, and other fluids, the fluid flows may be modeled through numerical simulation. Numerical reservoir simulation is often used to plan the development and operation of oil and gas reservoirs. The hydrocarbon reservoirs containing oil and gas are made productive by drilling boreholes or wells, referred to as producers or production wells.
As hydrocarbons are produced, reservoir pressure can decrease making it increasingly difficult to recover more of the oil and gas. Additional boreholes may be drilled into the reservoir to inject fluids that dislodge and displace the remaining oil and gas and add pressure to sweep them towards producers. Boreholes that are used for injecting fluids are called injectors or injection wells, and they can inject a range of fluids from water to polymer solutions and from liquid propane gas to carbon dioxide gas. The most popular choice, for example, is to inject water to displace oil towards production wells—a process known as waterflooding.
Optimizing a waterflood or other injection operation requires continuous analysis of large amounts of oilfield data and corrective actions. Waterflood surveillance classically apportions an oilfield into patterns of wells as units to monitor performance. Typically, an injector and its neighboring group of producers (an injector-based pattern) or alternatively a producer and its neighboring group of injectors (a producer-based pattern) are considered as single units for monitoring various reservoir performance parameters. Some patterns are simply defined by an area containing several injectors and producers. The amount of oil, for example, associated with a pattern—oil that has been displaced and oil that is remaining—is a key performance indicator. Other key indicators are the amount of oil and water produced and the average pressure of the pattern maintained by water injection.
Operators manage the performance of waterflood and injection operations by judiciously allocating injection and production capacity among the various patterns. But hydrocarbon reservoirs are geologically very heterogeneous. The data used to model such reservoirs is very limited and uncertain resulting in several equally likely models.
Streamline simulation is a numerical simulation method that has unique benefits for the modeling of injection-related recovery methods. First, it can accurately and efficiently simulate the displacement process in high resolution models of complex reservoirs. Second, streamline simulation produces information that directly quantifies the relationship between injectors and producers. Flow of fluids from injectors to producers is computed along streamlines that trace the movement of fluid particles. Well-rate allocation factors are a natural byproduct of streamline simulation. There is a strong visual component attached to the analysis of such information that is essential for management of waterflood operations. However, when reservoir models are large and complex and contain many wells, then current visual analysis systems can be cumbersome and error prone. What is needed is a system for visualizing producer-injector relationships and fluid flow along streamlines that are appropriate for large and complex reservoir models.